1915-013: 9 February 1915

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INTERSTATE COMMERCE COMMISSION.

REPORT OF THE CHIEF OF THE DIVISION OF SAFETY COVERING INVESTIGATION OF AN ACCIDENT ON THE CHICAGO, MILWAUKEE & ST. PAUL RAILWAY AT OAKWOOD, WIS., FEBRUARY 9, 1915.

May 27, 1915.

To the Commission:

[¶1]  On February 9, 1915, there was a derailment of a freight train on the Chicago, Milwaukee & St. Paul Railway at Oakwood, Wis., which resulted in the derailment of 29 cars, 11 of which, together with the station building, were destroyed by fire. After investigation as to the nature and cause of this accident, I beg to submit the following report:

[¶2]  The division on which this accident occurred is a double-track line, trains being operated under the automatic block-signal system. Approaching the point of derailment from the east the track is straight, with a slight descending grade. The weather was clear.

[¶3]  The train involved in this accident was westbound freight train extra 8167, consisting of 75 cars and a caboose, hauled by locomotive 8167, and was in charge of Conductor Jones and Engineman Christoph. It left Galewood, Ill., at 7.25 p.m., and at about 10.33 p.m. was derailed at the frog of the house-track switch near the station at Oakwood, while moving at a speed estimated to have been about 25 miles per hour.

[¶4]  Examination of the track showed that the first indication of anything wrong was at a point about 1 mile east of Oakwood, where an oil box, brass, packing waste, etc., were found on the east side of the track. About 370 feet west of this point the rear truck under Missouri, Kansas & Texas box car No. 60628, the tenth car in the train, left the rails and ran along on the ties until the frog at the house track was reached, where the other 28 cars were derailed. The oil box, etc., were found to have come from the rear truck of the box car, the partial destruction of the truck at this point evidently having been due to the defective condition of the wheels under the truck. Three of the four wheels were defective, the left forward wheel being the only one intact. The others had flat spots, broken flanges, etc.

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[¶5]  Investigation developed that this car was received from the Belt Railway at Chicago in a transfer train at 5.35 p.m. on February 8. Before this train was broken up and switched around all the cars in the train were inspected and, although wheel defects were found in other cars, none was found under car No. 60628. Although this car was again inspected by two car inspectors, one safety-appliance man, and two oilers before being sent out, no defects were discovered.

[¶6]  Engineman Christoph stated that as his train was approaching Oakwood he looked back and noticed fire flying from under the train, and at once made an application of the air brakes, at about which time the derailment occurred. Previous to this he did not notice anything wrong. At Wadsworth, a station 30 miles east of Oakwood, the train was inspected by the brakemen, but nothing wrong was discovered at that time.

[¶7]  This accident was caused by the defective condition of wheels in the rear truck of Missouri, Kansas & Texas box car 60628. This defective condition resulted in the partial destruction of the truck and its subsequent derailment.

[¶8]  The examination to determine the reason for the failure of the wheels under this car was conducted by Mr. James E. Howard, engineer physicist, tests being made in conjunction with representatives of the Chicago, Milwaukee & St. Paul Railway at the shops of that company in Milwaukee, Wis. The report covering the results of this investigation is as follows:

REPORT OF THE ENGINEER PHYSICIST.

[¶9]  The chilled-iron wheels in use under Missouri, Kansas & Texas Lines box car No. 60628, which led to the derailment of train No. 8167, at Oakwood, Wis., February 9, 1915, were 33-inch wheels branded as follows:

[¶10]  On their outside faces—

Mount Vernon Car Mfg. Co., Mt. Vernon, Ill., M. C. B. 1907.

[¶11]  On their inside faces—

Designation of wheel:	Brand marks.
1	32 K F 144792 Aug. 5/10 M. K. & T. Wt. 615 lbs.
1a	25 R F 144377 Jul. 30/10 M. K. & T. Wt. 615 lbs.
2	29 K F 144811 Aug. 5/10 M. K. & T. Wt. 615 lbs.
2a	25 R F 144964 Aug. 6/10 M. K. & T. Wt. 615 lbs.

[¶12]  Wheels designated Nos. 1 and 1a were on the forward axle of the truck; Nos. 2 and 2a were on the rear axle. Those with plain numerals were on the right-hand ends, while those with the subletter “a” affixed were on the left-hand ends of the axles, according to the direction the train was traveling.

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[¶13]  Each of the right-hand wheels had deep flat spots worn on their treads, with parts of their flanges broken off at places circumferentially immediately to the rear thereof.

[¶14]  The flange on the left-hand wheel of the second axle was broken at a place one-quarter of the circumference back of the break in the flange of its mate. The forward left-hand wheel was intact, the only uninjured one on the truck.

[¶15]  Figures Nos. 1 and 2 show the truck as it appeared after its removal from the place of derailment and transfer to the yard of the Chicago, Milwaukee & St. Paul Railway at Milwaukee. It received

considerable injury on the occasion of the derailment. The oil box of the rear axle, right-hand side, was gone, bolt heads were sheared off, and parts of the frame distorted, occurring in part probably after the wheels had left the rails. The destruction of the oil box, it is believed, was brought about by the condition of the rim of the wheel, and was an event which immediately preceded the derailment. At each rotation of the wheel the axle must have wabbled a very considerable amount, as the subsequent examination showed. This was the case with both right-hand journals of the truck, due to the eccentricity of the treads of the wheels at those ends.

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[¶16]  The flat spots on wheels Nos. 1 and 2 were 3/8 inch and 5/16 deep, respectively, measured from the shoulders of the outer parts of the treads, and each were 11 inches long. In width these spots formed grooves, somewhat wider than the head of a 100-pound rail, the inner edges of which coincided with the flanges of the wheels.

[¶17]  The endwise drift of each axle was toward the right, which resulted in flange wear of the right-hand wheels, with the absence of such wear on the opposite ends. The endwise drift of the axles and shoulders at the flat spots of the wheels appear cogent reasons for

the occurrence of the broken flanges at the particular places where they were found, while the wabbling of the journals sufficiently accounts for the general destructive effect witnessed in the truck.

[¶18]  In the examination of the wheels the radii of the treads were measured when the axles were mounted on dead centers in a lathe. The journals of both axles ran nearly true, the conditions attending the derailment not having sprung them materially. The radii of wheels Nos. 1 and 2, measured in a plane 3 inches from the outside of the rim, were as follows:

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Station.	Radii.		Station.	Radii.
	No. 1. Inches.	No. 2. Inches.		No. 1. Inches.	No. 2. Inches.
1	16.04	16.10	8	16.37	16.35
2	16.27	16.25	9	16.37	16.34
3	16.30	16.37	10	16.39	16.35
4	16.31	16.37	11	16.40	16.34
5	16.31	16.37	12	16.40	16.32
6	16.31	16.35	13	16.40	16.30
7	16.35	16.35	14	16.38	16.30

[¶19]  The maximum variation in the radius of wheel No. 1 was 0.36 inch; in that of No. 2 it was 0.27 inch. The shoulder abreast the worn spot of No. 2 was a little above the circumference of a circle described by the maximum radius in the plane of these measurements. The mates of these two wheels ran fairly true on their treads, while the flanges of all four wheels ran well.

[¶20]  Two unsatisfactory conditions pertained to the wheels of this truck, (1) the flat spots which caused a variation in radius, as above shown, and (2) differences in the peripheral lengths of the mated wheels. With each rotation there was a vertical movement of the right-hand journals, and, due to the difference in circumferences of the wheels on the same axle, one had a tendency to travel over a different length of rail than the other.

[¶21]  The vertical travel of journal No. 1 per mile of track would aggregate about 18 feet; that of No. 2 nearly 13 feet, with oscillations for train speeds of 25 miles per hour occurring at a rate somewhat above four per second of time.

[¶22]  The circumferences of the four wheels and the differences of those on the same axle were as follows:

Number of wheel.	Circum­ference. Inches.	Difference. Inch.
1	102.73	0.34
1a	103.07
2	102.60	0.51
2a	103.11

[¶23]  These differences are seen to be substantially three and four “tape sizes,” respectively. Per mile of track the larger wheels of the mates would to travel the greater distances of 17.4 and 26.1 feet, respectively. The distance this car was hauled from the Galewood yard to the place of derailment, 70.7 miles, would therefore call for aggregate differences approximating one-fourth of a mile and one-third of a mile for the two axles. Such were the conditions which prevailed [Page 6 - Top of Report] at the time of derailment. The wheels were not serviceable, and their appearance indicated that a considerable interval of time had elapsed since they had been in a proper condition for use.

[¶24]  The inquiry was conducted along lines to ascertain the physical state of the metal of the wheels in respect to depth of chill and hardness of the treads. Questions of strength did not enter as a factor, the manner of failure being such as to exclude strength as a direct consideration. The flanges of three of the wheels are broken, fragments

being detached in detail. These were secondary matters, it is believed, induced by the flattened and grooved treads.

[¶25]  The wheels were pressed off the axles, after which they were taken to a foundry breaker, there broken, and the fractures examined. The force required to remove the wheels from their axles ranged from 50 to 60 tons. The diameters at the wheel fits were 5-3/4 by 7 inches long. Although the wheels were firmly attached to their axles, the latter were rusty over parts of their length, indicating irregular boring or turning, with places where the axles did not fill the hubs [Page 7 - Top of Report] of the wheels. In the hub of wheel No. 1a the axle was rusty the greater part of its length, indicating a very short length of fitted surface.

[¶26]  The fragments of the wheels showed a limited depth of chill, excepting wheel No. 1a. There was practically no chilled metal below the worn spots of the treads of wheels Nos. 1 and 2. Some chilled iron remained in other parts of the treads. It ranged from 1/8 inch at the throat to 3/4 inch at the corner of the rim in wheel No. 1.

In wheel No. 2 the chill at the middle of the width of the tread, 21 inches circumferentially from the worn spot, was 3/16-inch.

[¶27]  On the left-hand ends of the axles, wheel No. 1a had a depth of chill of 5/8 to 1 inch. In No. 2a it ranged from 1/2 to 3/8 inch at the corners and about 3/16-inch in other parts of the tread.

[¶28]  The flat-worn wheels and one of the mates had “soft” chills, to which circumstance the worn spots are in the main attributed.

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[¶29]  Photographs Nos. 3 and 4 show the appearance of fractured portions of the rims in cross section of wheels Nos. 1 and 1a. These cuts represent fragments of the wheels which were made at the foundry breaker.

[¶30]  The chemical analyses of the metal of three of the wheels furnished by the Chicago, Milwaukee & St. Paul Railway Co. were as follows:

Number of wheel.	Phosphorus.	Manganese.	Sulphur.	Silicon.
1	0.351	0.65	0.207	0.73
2	.324	.63	.228	.71
1a	.350	.68	.205	.72

[¶31]  The contours of the four wheels are shown on diagram No. 5, on which are also entered the circumferences of each and the depths to which the right-hand wheels were locally worn. Measured radially, the amounts the two right-hand wheels ran out differ slightly from the depths locally worn on the treads. This result comes about from the shoulder not having the same radius as the comparison portion of the tread in the plane of the flat spot.

[¶32]  There was no evidence of thermal cracks in these wheels, nor were there indications present of their having been exposed to a high temperature during their term in service. The wheels were worn flat, as it appeared, by reason of the softness of the metal of the treads—the absence of chilled metal. If the “tape size” of a chilled wheel is a reliable index of the depth of the chill, then it would follow that usual inspection measurements, if made, must have shown the softness of these wheels. Therefore the period of their manufacture is believed to be accountable for their physical condition, while the responsibility for their continued use should be shared jointly by the different car inspectors through whose hands the car passed after the wheels had reached an unservicable state.

[¶33]  For comparative purposes other chilled wheels were examined, some of which had been exposed to exceptional conditions and had failed in service, while others had been removed on account of vertical flanges, shell outs, and comby treads. Two of the wheels examined, which contained defects resulting from service conditions, will be referred to in this report.

[¶34]  Figures Nos. 6 and 7 show two fragments, a large and a small one, from a wheel which fractured in service, at which time about one-third of the rim was detached. The wheel displayed evidence of having acquired a comparatively high temperature through brake action, its fracture being due without doubt to that cause.

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[¶35]  These particular fragments were made in a drop-testing machine during the examination of the general state of the metal.

[¶36]  Figure No. 6 is a sectional end view of the two fragments. There was a small thermal crack at the throat and a larger one separating the metal of the flange. The smaller one was oblique in direction, while the flange break was direct across the rim. There was a group of small cracks in the vicinity of the throat within an are partially covered by the magnetic oxide of iron. Other areas of magnetic oxide were present on different parts of the tread, in which thermal cracks were common. The presence of this oxide signified that the surface of the tread had been exposed to a comparatively high temperature.

[¶37]  Differences in depth of the color of the thermal cracks, illustrated in figure No. 6, leads to the inference that they had their origins at different periods, that the formation of the throat crack was antecedent to that of the flange, and that the latter was probably developed on the occasion of the final fracture of the wheel.

[¶38]  Figures Nos. 8 and 9 show the opposite ends of another fragment of the same wheel. A small thermal crack is shown on the fractured surface of figure No. 8 and a succession of short cracks on figure No. 9, all of which were located near the outside edge of the rim. They penetrated the tread varying depths, from one-eighth of an inch to five-eighths of an inch, each taking a general course crosswise the rim. In the vicinity of these cracks the surface of the tread presented a fine pebbled appearance, resembling the surface acquired at the bore of a gun after firing a number of rounds and consequent exposure to the high temperature of the powder gases.

[¶39]  In respect to the period of formation of cracks in the tread and those of the plates, it is believed that they are not of simultaneous occurrence, that plate fractures have their period of development at the time of maximum temperature of the rim; that is, when the difference in temperature between the rim and the plate is greatest. The rim at this time would be in compression while the plates were then in tension.

[¶40]  Thermal cracks in the tread, as well as those in the plates, are tension fractures. Their formation in the tread would be expected to occur when the immediate surface of the tread was rapidly cooled, after a period of heating and while the interior metal of the rim was still hot, in this manner reversing for a time the strains at the immediate surface and leading to the development of tension fractures.

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[¶41]  The critical period in the formation of cracks in the plates would coincide with the time when the brakes were acting, while that of incipient thermal cracks in the tread would be found in the interval immediately succeeding the release of the brakes. The extension of thermal cracks in the tread, according to this analysis, would be progressive. After incipient cracks had once formed in the tread the sudden heating of a cold wheel, through brake-shoe pressures, would, however, introduce conditions tending toward their further extension, thus constituting a difference between the starting of a crack in this part of the wheel and its subsequent extension.

[¶42]  These disruptive influences are inseparably connected with the service requirements of a wheel, and they explain why wheels exposed to severe service conditions are those which are most likely to fail. Braking conditions are prominent factors in the case.

[¶43]  The depth of chill in the wheel represented in figures Nos. 6 to 9, inclusive, ranged from 1 inch to 1¼ inches. Below the white chilled iron there was about 1¼ inches of mottled iron, beyond which gray iron was met. Some parts of the ribs of the wheel were white iron. The hub and plates were gray, excepting in the vicinity of the chaplets and core anchors, where, as not infrequently is the case, the metal was white.

[¶44]  The chemical analysis of the iron was as follows:

Carbon, total	3.50
Phosporus	.35
Manganese	.39
Sulphur	.155
Silicon	.41

[¶45]  The appearance of the fractured surface of another wheel is shown in figure No. 10, an endwise view of the rim. The thermal crack near the outer edge of the rim measured 1½ inches long by 3/4 inch deep and was located in a plane extending crosswise the tread. The minumum depth of chill was about ½ inch, with 1 inch of mottled iron between the white and the gray iron. This fragment came from a wheel selected at a foundry breaker.

[¶46]  Incipient cracks in materials which arethe result of service conditions cannot be regarded as undeserving of attention. Nevertheless, it must be recognized that there are probably many wheels of this type in service in which thermal cracks are present which have been caused by severe braking conditions. The possibility of their extension and development into a dangerous state is an important feature to be considered. The use of material which furnishes evidence of being overworked calls for the exercise of a discriminating judgment, presenting the alternative queries when to continue its use and when to recommend its rejection from service. Causes which are

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found to be common to derailments should without doubt be given earnest consideration.

[¶47]  In conclusion, the derailment of train No. 8167 appears to have been immediately due to the partial destruction of the rear truck of Missouri, Kansas & Texas box car No. 60628, which, in turn, resulted from the defective condition of the right-hand wheels of that truck. These two wheels had flat spots worn on their treads, causing excessive wabbling of the journals of the axles, which culminated in the destruction of the journal boxes, caused the car body to drop

upon the right-hand wheels, and when a frog in the track was reached precipitated the derailment of the train.

[¶48]  At the worn spots of these wheels there was practically no chilled iron present. At other parts of the treads the depth of chill was shallow. It is believed that these wheels in their original state had “soft” chills, which led to the early formation of the worn spots and constituted the primary causes of the derailment.

[¶49]  The worn condition of the treads was such as to indicate that they had been in an unserviceable condition for some time preceding the derailment.

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SUMMARY.

[¶50]  The examination of the wheels in the truck which was under Missouri, Kansas & Texas box car No. 60628 clearly fixed the immediate responsibility for this derailment on the worn treads of two of the wheels. These flat spots were not “slid flat” places, but were grooves 11 inches long each, worn in the treads, and having depths of three-eighths and five-sixteenths of an inch, respectively. The grooves were wider than the head of a 100-pound rail. The axles drifted to the right, in the direction of these wheels, which showed worn flanges, approaching vertical faces.

[¶51]  The examination also revealed the fact that these wheels had less depth of chill than customary in wheels of this type, and at the worn spots the chilled metal was entirely absent.

[¶52]  The lack of rotundity of the wheels was such that excessive wabbling of the journals occurred at every rotation, bringing undue strains on the truck frame. At usual speeds these oscillations took place several times a second, and they are believed to have been the cause of the injury to the truck and the immediate forerunner of the derailment.

[¶53]  Furthermore, the mated wheels were of different sizes. Those on the right-hand ends of the axles were three and four “tape sizes” smaller, respectively, than the left-hand wheels. These differences would tend to cause the truck to run in an oblique position, not square with the track, and also be the equivalent of a certain amount of braking power set against the train.

[¶54]  A conspicuous feature associated with conditions of these wheels is the fact that the inspections which had been made from time to time failed to detect the presence of the flat spots. These defects in the treads were undoubtedly of long standing, and the car must have passed quite a number of inspections since the wheels had become unserviceable. These defects were of such a nature that they should have been discovered by ordinary inspection.

[¶55]  In a previous report covering the investigation of a derailment of a passenger train, due to a broken wheel, attention was called to the alarming frequency of accidents due to broken wheels, and statistics covering a five-year period were published, showing that during that period the derailments attributable to defective wheels were approximately 31 per cent of the total number of derailments charged to defective equipment. In the commission’s Accident Bulletin No. 52 there is published a summary of derailments due to defects of equipment on steam railways for 13 years ending June 30, 1914. This summary shows that of 37,456 derailments due to equipment defects [Page 16 - Top of Report] 12,882, or more than 34 per cent of the whole, were caused by defective wheels. The property loss suffered by the railroads on account of these 37,456 derailments was $30,138,241, of which sum $12,506,766, or about 41.5 per cent of the whole, was attributed to derailments caused by defective wheels.

[¶56]  These figures indicate that defective wheels constitute one of the most prominent causes of derailments. In the interest of safety, as well as of economy, steps should be taken by the railroads to insure that sound wheels will be obtained from the manufacturers in the first instance; and methods of inspection should be adopted to prevent the placing in service of defective wheels and insure that wheels which have become defective through service shall be removed in ample time to provide for the safe operation of trains.

Respectively submitted,

H. W. Belnap,
Chief, Division of Safety.